[Feature]: surface per-target quota state in the combo workspace — disable actions when all targets have 0 credits

[lidge-jun]

Scope

Surface per-target quota state in the combo workspace and disable combo actions when every target has known zero remaining credit.

This issue is the workspace/UI child of #1711.

In scope

• Show per-target quota/exhaustion state in the combo workspace.
• Clearly indicate when all targets are exhausted.
• Disable actions that cannot succeed while every target has known zero credit.
• Re-enable those actions when quota state recovers.

Out of scope

• Catalog/model-picker inactive-state semantics: parent issue [Feature]: grey out zero-credit models/combos in the served model catalog and picker #1711.
• Runtime retry-loop prevention and candidate re-evaluation/failover: [Feature]: re-evaluate a routing profile when the selected candidate fails terminally #1572.

Implementation

• Related implementation PR: feat(gui): surface per-target quota state in combo workspace (#1702) #1704.

Relationship

• Parent: [Feature]: grey out zero-credit models/combos in the served model catalog and picker #1711
• Runtime failover owner: [Feature]: re-evaluate a routing profile when the selected candidate fails terminally #1572